1. Field of the Invention
The present invention relates to hoses, and, more particularly, to automobile hoses such as a gasoline fuel hose, fuel cell automobile hoses such as a methanol fuel hose and a hydrogen fuel hose, engine cooling hoses such as a radiator hose and a heater hose, and a refrigerant conveying hose such as used in a cooler.
2. Description of the Art
Conventional automobile hoses including a gasoline fuel hose utilize the following hoses (1), (2) and the like based on their battery liquid resistance, anti-chipping, flame resistance, and low cost. Hose (1) has an inner layer made of a polyamide resin, and an outer layer made of rubber comprising an ethylene-propylene-diene terpolymer (EPDM) formed on an outer peripheral surface of the inner layer. Hose (2) has an inner layer made of polyamide resin, an intermediate layer made of ethylene-vinyl alcohol copolymer (EVOH) formed on an outer peripheral surface of the inner layer, and an outer layer made of EPDM formed on an outer peripheral surface of the intermediate layer.
In the hose (1), the rubber outer layer is adhered to the outer peripheral surface of the polyamide resin inner layer with an adhesive. Due to unevenness of the adhesive coating, the rubber layer and the polyamide non-rubber layer tend to be adhered insufficiently, resulting in a decreased sealing property. In the hose (2), the rubber outer layer is adhered to the outer peripheral surface of the EVOH intermediate layer with an adhesive. Due to coating unevenness of the adhesive, the rubber layer and the EVOH non-rubber layer are adhered insufficiently, resulting in a decreased sealing property. In addition, for producing the above-mentioned conventional hoses (1) and (2), a step of coating the adhesive is required. Accordingly, the production becomes complex, costs are increased, a pot life and a concentration of the adhesive should be controlled. Thus, stable productivity of the hoses cannot be achieved. Furthermore, the adhesive typically is diluted with an organic solvent, i.e., toluene, which may cause environmental pollution.
Accordingly, it is an object of the present invention to provide a hose comprising a rubber layer and a non-rubber layer that adhere well to each other without applying an adhesive to an interface therebetween.
The present invention provides a hose, comprising a laminate including
a rubber layer comprising a rubber composition containing as essential components (A)-(D), wherein:
(A) a rubber made of at least one material selected from the group consisting of an ethylene-propylene-diene terpolymer and an ethylene-propylene copolymer,
(B) a vulcanizing agent containing a peroxide,
(C) a resorcinol compound, and
(D) a melamine resin; and
a layer made of at least one material selected from the group consisting of a polyamide resin, an ethylene-vinyl alcohol copolymer, and a metal.
The present inventors intensively studied providing a hose comprising a rubber layer and a non-rubber layer that adhere well to each other without applying an adhesive to an interface therebetween. The studies have investigated to an idea that an adhesive is mixed into a rubber composition which is used in the rubber layer. A combination capable of providing an excellent adhesion of the rubber and the adhesive has also been studied. As the rubber, EPDM and an ethylene-propylene copolymer (EPM) have been selected because they are relatively inexpensive. An adhesive containing certain components, i.e., a resorcinol compound and a melamine resin, then is mixed with the rubber, and is vulcanized using a vulcanizing agent containing a peroxide. When the mixed and vulcanized rubber layer is laminated with a non-rubber layer such as a polyamide resin layer, excellent adhesion between the layers can be obtained. Thus, the inventors attained the present invention. The reason why the rubber layer comprising the specific rubber composition adheres well to the non-rubber layer such as a polyamide resin layer is presumed as follows: The resorcinol compound functions mainly as an adhesive, while the melamine resin functions mainly as an adhesive adjuvant. The resorcinol compound receives a CH2O group from the melamine resin. The CH2O group is covalently bonded to a polyamide group (xe2x80x94CONHxe2x80x94) of the polyamide resin, EVOH, or a metal, thereby improving the adhesion. For example, the resorcinol compound represented by the following formula (C) receives the CH2O group from the melamine resin to provide the compound represented by the following formula (Cxe2x80x2). The compound (Cxe2x80x2) is covalently bonded to the polyamide group (xe2x80x94CONHxe2x80x94) of the polyamide resin as shown. It is considered that such covalent bond provides strong adhesion. Further, a portion of hydroxyl groups in the resorcinol compound are hydrogen bonded to the polyamide groups of the polyamide resin. The hydrogen bond also relates to improvement in adhesion. 
Moreover, when a mixing ratio of the resorcinol compound (C) and the melamine resin (D) is within a predetermined range, or when a mixing percentage of the resorcinol compound (C) to the specified rubber (A) is within a predetermined range, adhesion between the rubber layer and the polyamide resin layer is further improved.
According to the present invention, the hose comprises the laminate structure including the rubber layer comprising the specific rubber composition, and the non-rubber layer, i.e., the polyamide resin layer, the EVOH layer, or the metal layer. The rubber layer itself has an adhesive property, and therefore excellent adhesion between the rubber layer and the non-rubber layer can be obtained without applying the adhesive therebetween. In addition, in a method for producing the hose of the present invention, the method does not require a step of coating the adhesive, since no adhesive is used. Accordingly, pot life and a concentration of the adhesive need not to be controlled, and thus stable productivity is achieved. Furthermore, no organic solvent is used for diluting the adhesive, and therefore no environmental pollution is caused. In the production of the hose according to the present invention, vulcanization is performed using, not the conventional sulfur vulcanizing agent, but rather using the peroxide vulcanizing agent. Accordingly, no zinc oxide is used. Even though the rubber layer is used as an inner layer of the hose, hose failure such as clogging and liquid spill on a sealing portion can be avoided.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.